Along with development of electronic component technology and human-machine interface, mouse, keyboard or button-type user interface are unable to satisfy user's demand. Regarding a mobile computing device, the mouse, keyboard and buttons are not convenient operation interfaces, which occupy a certain space outside a screen, such that a volume of the mobile computing device is hard to be reduced.
In this case, a touch panel technique is quickly developed. A touch panel is generally disposed in front of a screen, such that a user may have a feeling of operating objects displayed on the screen. Based on such intuitive operation method, even elders or children who are not accustomed to use a mouse and keyboard can learn to use the touch panel quickly, and therefore the touch panel is widely welcomed by consumers.
The existing touch panels may include capacitive touch panels, resistive touch panels, optical touch panels, etc. according to different operation principles thereof, where the capacitive touch panels are widely applied in mobile computing devices due to its high sensitivity.
However, human pursuit of technology product is endless, and in a next generation, flexible touch screens are probably welcomed by consumers. In order to match a flexible display, the touch panel should also be made flexible, and a glass substrate in the touch panel is required to be changed to a flexible substrate, for example, a plastic substrate. However, the plastic substrate is liable to be yellowed under high temperature of the fabrication process, which may result in a yellowing phenomenon of the whole flexible touch sensor, and decrease a color performance of the flexible touch screen.